Tom Volk's Fungus of the Month for August 2000

This month's fungus is Hohenbuehelia petaloides, a wood decay fungus that eats nematodes

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Hohenbuehelia petaloides This month's fungus is interesting in many ways. First of all is the interesting name, pronounced hoh-in-buhh-HEEL-ee-uh petal-OID-ees. It's named after Ludwig Samuel Joseph David Alexander von Hohenbühel Heufler (1817-1885) who is described as having been an Austrian statesman and botanist/mycologist. I'll tell you more about him later. (Thanks to Richard Aaron of Toronto, Canada for this information! He knows everything about where these names come from.) Hohenbuehelia is reported to be edible, but rather tough and not particularly delicious. Ecologically it is a wood decay fungus. I usually find it on very rotted wood. More about that later.

So, you say this mushroom looks a whole lot like the oyster mushroom, Pleurotus ostreatus? Well, it used to be included in the genus Pleurotus because of the way it looks macroscopically-- But you'll see later there are some important differences. Although you can call both of them mushrooms, Hohenbuehelia and Pleurotus are not configured in the same way you would think of as a typical mushroom-- there's often no stem and when there is a stem it's usually rather small and attached laterally or eccentrically! The Hohenbuehelia mushroom, (or fruiting body or basidiome, depending on whose terminology you want to use) has very narrow, crowded gills that are decurrent, or run down the stem. It usually has much narrower flesh than Pleurotus. There are also some significant microscopic differences between the two genera.

Hohenbuehelia cross section of capThe easiest way to distinguish Hohenbuehelia from Pleurotus is that Hohenbuehelia has a gelatinous layer between the context (flesh) of the mushroom and the cap cuticle, as shown in the picture to the right. The upper left hand corner is the outside of the top of the mushroom. Below the cuticle you can see some roughly parallel hyphae embedded in a gelatinous matrix. This gelatinous layer makes this mushroom much more rubbery and tougher in texture. Below that is the context, or flesh of the mushroom, and below that would be the gills.

In the picture below is another distinguishing feature of Hohenbuehelia; it has metuloid cystidia in the hymenium. Cystidia are sterile structures between the basidia that probably serve to separate the gills, act as places to dump wastes, or protect from insect predators. If you've been paying attention to these pages you may have seen the spectacular cystidia of Pluteus cervinus, which was Fungus of the Month in June of 1998. You'll notice the cystidia below do not have the horns found on Pluteus and these are much thicker. These also have thicker walls and a dense coating of crystals on their surface (that's what makes them metuloid cystidia). Most of the crystals have fallen off during the preparation of this specimen.

Incidentally, both of these microscopic pictures were taken with my digital camera (Nikon CoolPix 950) through the eyepiece of a normal microscope, without any attachments and without removing the eyepiece. It's so easy. Make sure the automatic flash is turned off. It's a very cool technique tip I got at a conference last year. Try it yourself!

Hohenbuehelia metuloid cystidium What about the wood decay I alluded to earlier? And what about the nematodes? Well as you might know, wood is a good source of carbon but a terrible source of nitrogen, which fungi need to make proteins. Both Hohenbuehelia and Pleurotus can supplement their protein needs by trapping nematodes, which are small flat worms that are very abundant in wood and soil. The fungi have "sticky knobs" on the hyphae that grow through the wood. These sticky knobs attach to curious nematodes as the nematodes attempt to eat the mycelium. The nematode thrashes around and additional parts of its body become stuck. The hyphae then grow into the body of the nematode and digest it, providing the fungus with the nitrogen it needs. That makes these fungi carnivorous!

There's another fungus, Arthrobotrys, that is famous for the snares it produces to trap nematodes, but that will have to be the subject for a future fungus of the month.

Here's a little more about the person the genus was named after. The following facts were taken primarily from Taxonomic Literature (Stafleau & Cowan) and were sent to me by Richard Aaron of Toronto:

"Prior to receiving a baronetcy in 1865, he published under the surname "Heufler" and his full name was:

Ludwig Samuel Joseph David Alexander Heufler zu Rasen und Perdonegg

After receiving the baronetcy in 1865, he published under the surname "Hohenbühel-Heufler" in his scientific publications. At this point, his full name became:

Ludwig Samuel Joseph David Alexander Freiherr von Hohenbühel Heufler zu Rasen und Perdonegg

The name in the introductory paragraph above -- Ludwig Samuel Joseph David Alexander von Hohenbühel Heufler-- was taken from Biographical Dictionary of Botanists Represented in the Hunt Institute Portrait Collection (1972). It represents a fair compromise if one has to give him just one name. It's the one I would use.

According to the most detailed source, he was an Austrian cryptogamist and state official. From the bibliography provided, I note that he published a work on a genus of European ferns. It is not clear from the other Germans titles what else he wrote about, although the word 'pilze' (mushrooms) never makes an appearance. This was also an oblique reference to the fact that he had a huge herbarium, which included specimens of algae.

The genus Hohenbuehelia was coined in 1866 by S. Schulzer von Müggenburg. He must have been quite respected in his time (even before he received the baronetcy) because he also had the following genera named for him (all based on his pre-baroneal name): Heuflera, Heufleria, Heufleridium (all listed in Dictionary of Fungi, 8th ed.)"

Thanks to Richard Aaron for researching this information. This goes to show you that there's always an interesting story behind every name. If you get the chance to learn about where names come from it might help you to learn them and appreciate them more.

I hope you enjoyed this month's fungus. I should also mention that you can distinguish it from similar looking brown-spored Crepidotus species by their white spore print. There are also several similar species of Hohenbuehelia that are difficult to distinguish without a microscope to look at the spore sizes. So far as I know no poisonings have been reported. But also there have been no spectacular dining experiences reported either.

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